2017 F-150 supercrew question
 

Can you open the rear suicide door when either of the front full-size doors are closed?

will it open but damage anything only once for emergency reasons or will it function and release the front closed door to be able to exit and have to push both doors open?

The front door latches to the rear door, the rear door latches to the top and bottom of the cap, the rear door is physically behind the front door. I do not know how you would force the rear door open with the front closed. I suppose with the jaws of life it could be opened. I would recommend getting a life hammer to break glass if you are concerned, screw it down somewhere you can access it, I always chuckle when I see one in someone's door pocket loose with all the other stuff that I assume will fly around the cab during a wreck bad enough that the life hammer is needed.